The reason Trump announced so early is some of his court cases are winding up and he is losing badly. He thinks he can claim they are political., and have them delayed. The fact is NY has him dead to rights for financial corruption and tax evasion. His people in the organization are saying he knew and approved it all. Every day in court, the noose tightens.
In Georgia, he is being charged with election interference and other crimes.
https://www.washingtonpost.com/national-security/2022/07/27/trump-georgia-investigation-explained/ They have him on the phone in the act.
They also are after his fake electors scam.
Trump's early announcement, the earliest ever, is a desperate attempt to thwart justice. However, there is nothing that says a candidate cannot face charges for crimes.